Automation Editor vertical quantisation

[Monospace-V]

Enhancement Summary

Much like there is vertical zoom and horizontal quantisation (snapping) of automation editor's points, there should be vertical quantisation (value snapping) of automation editor's points.

Justification

The most specific use case can be pitch bending for plugins that don't support in-piano roll pitch bending, wherein instead of carefully trying to ensure you bend the correct amount, there is automatic snapping. This can be done with a "Snap to multiples of x" option.
(However, sometimes we want a detuned instrument doing normal pitch bending, in which case there could be an option "Snap to multiples of x + n" where n is the detuned amount. But that is extrapolation.)
Y-axis snapping of automation editor values is a useful tool.

Mockup

[Spekular]

#5923 means this is now always doable (just slow), and fixing #4313 would further mitigate it. This is still a good proposal IMO, but I would personally prioritize better zoom.